1. Renal Replacement Therapies
Renal Replacement Therapy (RRT) can be performed in specialized dialysis centers for treatment of chronic patients that have permanently lost kidney function and in hospitals for treatment of patients with a need for temporary replacement of renal function. Different modalities of Continuous Renal Replacement Therapy (CRRT) have been used to treat patients suffering from excess fluid overload and acute renal failure. In acute settings, CRRT has been performed using standard methods of hemodialysis and continuous arterio-venous hemofiltration (CAVH). More recently, continuous veno-venous hemofiltration (CVVH) has been used to reduce the complications associated with such issues as hemodynamic instability and need for arterial access. Regardless of the type of medical equipment used and the specific type of treatment performed, RRT requires establishing an extracorporeal blood circulation path that passes blood through a filtration device.
RRT performs two primary blood treatment functions: ultrafiltration (removal of water from blood plasma), and solute clearance (removal of different molecular weight substances from blood plasma). RRT involves the use of a filter in a blood circuit through which circulates extracorporeal blood temporarily withdrawn from a patient. The RRT filter, also called hemofilter or dialyzer, can be set up to perform either or both of these functions simultaneously, with or without fluid replacement, accounting for the various modes of renal replacement therapy. “Clearance” is a term that describes the removal of substances, both normal and waste product, from blood.
Ultrafiltration is the convective transfer of fluid out of a plasma compartment of a filter and through pores in the filter membrane. The pores of the filter membrane pass (filter) water, electrolytes and small and middle-sized molecules (up to 20,000 to 30,000 daltons) from the blood plasma. Large molecules, proteins blood cells and other large-sized plasma components (as well as a portion of the water and smaller components) do not pass through the filter membrane and remain in the plasma compartment of the blood circuit and are returned to the patient. The ultrafiltrate output (e.g., water extracted from the blood) from the filtration pores is similar to plasma, but without the plasma proteins or cellular components. Since the concentration of small solutes is the same in the ultrafiltrate as in the plasma, no clearance is obtained from the plasma, but fluid volume, e.g., water, is removed.
Dialysis is the diffusive transfer of small solutes out of a blood plasma compartment of a filter by diffusion across the filter membrane. This transfer occurs as a result of a concentration gradient, with diffusion occurring from the filter compartment with higher concentration (typically the blood compartment) to the filter compartment with lower concentration (typically the dialysate compartment). Since the concentration of solutes in the plasma decreases, clearance is obtained, but fluid may not be removed in dialysis. Ultrafiltration can be combined with dialysis to obtain both clearance and fluid removal from blood plasma.
Hemofiltration is the combination of ultrafiltration and fluid replacement in the treatment of blood. Typically, hemofiltration treating larger volumes of blood than is needed for fluid control. The replacement fluid contains electrolytes, but not other small molecules. Since the net effect of replacing fluid without small solutes and ultrafiltration of fluid with small solutes results in net removal of small solutes, clearance is obtained during hemofiltration.
2. Limitations of User Interface of Existing Devices for RRT
RRT devices use sets of disposable blood passage circuits (generally referred to as “disposables”) generally including tubing, filters, catheters, sensors and connectors that form a fluid circuit and are in direct contact with the blood and the fluid removed from the blood. These disposables can be assembled from components made by various manufacturers. Some more expensive disposables such as dialyzers can be used several times to treat the same patient. In some cases, disposable sets come assembled and the user need only mount the disposable blood passage on an instrument and pumping machine, and then prime the blood passage with sterile saline solution prior to its use. When the RRT device is ready for use, it is connected to the network of disposable and fluid filled tubes and electronic sensors that include the disposable blood passageway.
Modern RRT devices are microprocessor controlled. The microprocessor operates pumps, reads sensors and communicates with the user via a user interface regarding the RRT treatment. In more advanced RRT devices, the user interface has a graphics display that may be a touch screen or have an associated keypad. By interacting with a display and keys, the user interface enables a user to control the RRT device and monitor its operation.
During the operation, the RRT device detects conditions that trigger alarms and require user intervention. These alarms may occur often. For example, joints between parts in the blood passage disposable can spring leaks, allowing the ingress of air and facilitating clotting. Clotting of blood often occludes the blood passages. These RRT devices incorporate pressure sensors that enable them to detect disconnection and occlusion of tubing and components of the blood circuit. Air and blood leak detectors are also used to detect other alarm conditions that require immediate action from the user.
To operate RRT devices, a high degree of skill is required from users to troubleshoot the causes of alarms and promptly rectify the condition that provoked the alarm. A quick response from the user is needed because the RRT device is usually stopped as a result of the alarm, and within minutes the blood in the circuit may coagulate. Generally, when an alarm condition occurs, a user will receive an alarm notification and an alarm code from the RRT device. For example, code “E001” may be displayed on a numeric display. The user will interpret this as an alarm code by remembering that “E001” is a particular alarm or by consulting a manual for the RRT device that defines the display codes for the device. In the latest generation of RRT machines, less cryptic text messages are presented that describe alarm conditions. Instead of flashing an alarm code E001, for example, the RRT device displays a message such as “Infusion Tubing Disconnected”. This plain language alarm message methodology is effective, but is still not intuitive to less-trained operators of the RRT device. Also, in the global marketplace, confusion often results from a language barrier and non-English speaking operators have difficulty with English language messages.
U.S. Pat. No. 5,858,239 discloses a dialysis machine that has a graphics display where a user is assisted by simple pictograms similar to “icons” used by the commonly used Microsoft Windows™ personal computer operating system. Another user interface that makes use of graphical icons instead of or complimenting text messages is disclosed in U.S. Pat. No. 5,620,608 for a dialysis machine. Although these icons help a user of a dialysis device navigate through a menu system, they are not helpful in troubleshooting faults in the blood fluid path of the device. A graphics user interface for an aphaeresis blood processing apparatus using pictorials is disclosed in U.S. Pat. No. 5,653,887, which displays icons and a symbolic diagram of the apparatus with an arrow pointing towards an element (blood centrifuge) requiring user attention. However, the graphics user interfaces disclosed in the prior art lack the ability to clearly direct a user to the specific point in the blood fluid path where an occlusion has been detected or the blood flow continuity has been broken.